The World Health Organization (WHO) recently published a series of background documents on different viruses, bacteria, and parasites to inform the revision of drinking water quality guidelines and guidelines on sanitation and health. Covered pathogens include Salmonella, Yersinia, Vibrio, Escherichia coli, Toxoplasma gondii, hepatitis A virus, hepatitis E virus, Campylobacter, and Shigella, among others.

The background documents include information about the strength of evidence linking the microorganisms to waterborne transmission, the presentation of illness, the burden of disease, infectivity, available detection methods, where the pathogens are often found, approaches for managing risk, effectiveness of water treatments, and whether E. coli is a suitable indicator organism.

According to the background documents, pathogens for which there is “strong evidence” linking transmission with unsafe drinking water include diarrhoeagenic E. coli, typhoidal and non-typhoidal Salmonella, Campylobacter, Vibrio cholerae, Shigella, Toxoplasma gondii, Cryptosporidium, Giardia duodenalis, Entamoeba histolytica, rotaviruses, hepatitis A, and hepatitis E.

Yersinia enterocolitica, Cyclospora cayetanensis, Helicobacter pylori, Burkholderia pseudomallei, and sapoviruses were identified as having “moderate evidence” for waterborne transmission. The strength of evidence that Staphylococcus aureus, Cronobacter sakazakii, and astroviruses are transmitted through drinking water is considered weak, and therefore, are of low health concern for drinking water.